Building products have utilized granule coated or embedded surfaces in a variety of anti-slip, weather-resistant, fire-resistant, and decorative surface applications. These building products include asphalt and non-asphaltic materials.
Asphalt building products may comprise felt or fabric stock impregnated with asphalt and covered with weather resistant mineral granules. Some examples of asphalt building products include asphalt shingles, asphalt siding, and rolled roofing. Typically, rolled roofing comprises modified bitumen asphalt including a polymer filling and asphalt roofing shingles comprise non-modified bitumen asphalt, which may include limestone as an additive. Alternatively, rolled roofing may comprise non-modified bitumen asphalt. Modified bitumen asphalt shingles have also been contemplated. Typical asphalt products have a glass or polyester substrate and a multitude of granules placed thereon and have served as relatively inexpensive alternatives to tile, slate and wood building products.
The granules serve to protect and provide coloring to the asphalt building product. For instance, granules serve to provide coloring to shingles and rolled roofing products and thus to the roof. Additionally, the granular material generally protects the underlying asphalt coating from damage due to exposure to light, in particular ultraviolet (UV) light. That is, the granules reflect light and protect the asphalt from deterioration by photo-degradation. In addition, such granular material improves fire resistance and weathering characteristics. In general, granules are embedded in the coating asphalt by the application of pressure and are retained therein by adherence to the asphalt.
Non-asphaltic building materials, such as plastic siding panels for surfacing walls and roofs of buildings, may comprise extruded or pressed thermo-plastic materials such as polyvinylchloride (PVC). Plastic flooring is another example of non-asphaltic building materials. Similar to asphalt building products, non-asphaltic building products comprising coated or embedded granules can have improved fire resistance, weathering characteristics and aesthetic appearance.
Good adherence of the granules to the building product is beneficial. In the case of some asphaltic roofing products, loss of granules reduces the life of the roof, since it is associated with acceleration of photo-degradation of the asphalt. In addition, the aesthetics of the roofing system may be compromised if granules are lost.
Granule loss can occur due to physical abrasion of the granular surface. This may occur during installation of the building material product; during maintenance; or may result from environmental conditions. Building products are especially susceptible to granule rub loss and tracking at elevated temperatures, in which granule loss and tracking may occur when an individual walks on the roof, leaving footprints or scuffs permanently imprinted into the roofing or walk on the building product while it is stored or shipped.
In asphalt building products, as granules are secured to the asphalt surface, there is a tendency for oils in the asphalt surface to creep onto or be adsorbed on the granules' surfaces. This creeping or adsorption of the asphalt oils on the granules' surface causes discoloration or staining of the granules and hence reduces the building material products aesthetic effect.
In one embodiment, the present invention provides granular surface building products, and a method of producing same, having increased protection against granule rub off, improved resistance to tracking, and improved resistance to discoloration than previously known in granular surface building materials.